Mac OS X: Today Apple is releasing FaceTime for OS X (in beta), allowing OS X and iOS users to quickly and easily video chat regardless of device.
You can start making FaceTime video chat calls to any iOS user (the iPhone 4 and fourth generation iPod touch) and other OS X users sometime today, as soon as Apple pushes their beta release. The download page isn't up yet is up here. There's very little to it beyond that. FaceTime video chats look like they work pretty seamlessly between iOS and OS X.
FaceTime for Mac beta is a free download in beta, available for download now.
FaceTime for OS X [Apple]